1. Field of the Invention
The present invention relates to a water temperature sensor for an air conditioner of automotive vehicles, and more particularly, to a water temperature sensor for an air conditioner of automotive vehicles, which is mounted inside an air-conditioning case for measuring the temperature of cooling water of a heater core, thereby preventing an air leakage from a mounted position of the water temperature sensor, enhancing work efficiency and productivity by reducing the number of components and the number of work processes, and providing efficient air-conditioning effect by greatly improving a response to heat around the sensor and a degree of precision in temperature measurement.
2. Background Art
In general, an air conditioner is installed inside an automotive vehicle for providing a passenger with an agreeable environment in various weather conditions or traveling conditions. Such an air conditioner is a device which exchanges heat by selectively passing air, which is introduced into an air-conditioning case by a blower unit having a blast fan, through an evaporator in which refrigerant flows or a heater core in which cooling water of a vehicle engine flows, and then distributes the air of a cooled or heated state through vents fluidically communicating with air discharge holes in various directions inside the vehicle to thereby cool or heat the inside of the vehicle.
In addition, the air conditioner includes an automatic temperature controlling device (FATC) as a means for controlling the indoor temperature of the vehicle to the optimum state according to temperature changes inside and outside the vehicle. The automatic temperature controlling device controls various module motors (a mode door motor, a temp door motor, and an indoor and outdoor air door motor) through a logical operation performed by a microcomputer after receiving input signals from various sensors for sensing the indoor air temperature, the outdoor air temperature and water temperature of the evaporator and the heater core, and from control switches, so that the automatic temperature controlling device keeps a driver's set temperature state of the indoor temperature.
Here, the sensor for sensing water temperature of the heater core (hereinafter, referred to as ‘water temperature sensor’) is mounted on the outer surface of the heater core to sense the temperature of the outer surface of the heater core so as to detect the cooling water temperature inside the heater core.
FIG. 1 illustrates a structure of the prior art water temperature sensor.
As shown in FIG. 1, the water temperature sensor 100 includes: a housing 101 adapted to be in contact with the outer surface of the heater core; a thermistor 102 embedded inside the housing 101 for changing a resistance value depending on the temperature transmitted from the housing 101; a lead wire 103 connected to the thermistor 102 and surrounded partially by an insulating tube 104; a connector 106 electrically connected to a controller (not shown) of the automatic temperature controlling device via a terminal section 105 coupled to an end portion of the lead wire 103; and a clip 107 formed integrally on the connector side and fixed at a predetermined portion of the outside of an air-conditioning case 200 (see FIG. 2).
The housing 101 is opened at the upper part and filled with epoxy resin 108 for molding, and a portion of the housing 101 where the thermistor 101 is connected with the lead wire 103 is fixed by epoxy resin 109 for coating.
That is, the water temperature sensor is manufactured through the steps of inserting the thermistor 102, which is connected with an end of the lead wire 103 fixed by epoxy resin 109 for coating, into the housing 101 filled with the epoxy resin 108 for molding and applying heat to the housing 101 to harden the epoxy resin 108 for molding.
As shown in FIGS. 2 and 3, such a water temperature sensor 100 is arranged to be in contact with the outer surface of a tank part 201a of a heater core 201 through a box-like sensor insertion space 200a, which is cut at the lower side of an air-conditioning case 200 having the heater core 201 therein and protrudingly formed on a portion opposed to the outer surface of the tank part 201a of the heater core 201, and then, fixed by a clamp 210 inserted between the air-conditioning case 200 and the heater core tank part 201a. 
As shown in FIG. 3, the clamp 210 includes a substantially straight type main body 211, a fixed section 212 bent at a longitudinal end of the main body 211, and a number of pressing sections 213 inclinedly protruding from the main body 211 toward the tank part 201a of the heater core 201. The clamp 210 is located between the housing 101 of the water temperature sensor 100 located on the outer surface of the tank part 201a of the heater core 201 embedded in the air-conditioning case 200 and the lower side of the air-conditioning case 200, has the upper portion of the main body 211, which is in close contact with the lower side of the air-conditioning case 200, presses the housing 101 of the water temperature sensor 100 toward the outer surface of the tank part 201a by the pressing sections 213, and is constricted on the lower side of the air-conditioning case 200 having the sensor insertion space 200a, whereby the housing 101 of the water temperature sensor 100 is fixed.
As described above, the water temperature sensor 100 has an end portion fixed by the clamp 210 and the other end portion fixed on the outer surface of the air-conditioning case 200 in an exposed state from the sensor insertion space 200a by the clip 107 as shown in FIG. 2.
However, the structure of the prior art water temperature sensor 100 has several problems in that it is complicated in mounting work and deteriorates operational efficiency and productivity due to an increase of work processes since the water temperature sensor 100 is fixed by the clamp 210 after the thermistor 102 is inserted into the sensor insertion space 200a formed in the lower part of the air-conditioning case 200.
Moreover, the prior art has another problem in that air-conditioning performance is deteriorated due to an air leakage to the outside through the sensor insertion space 200a since the sensor insertion space 200a for mounting the water temperature sensor 100 therein is separately cut and formed in the lower part of the air-conditioning case 200.
To prevent the air leakage, a sealing member (not shown) may be mounted on the sensor insertion space 200a, but in this instance, it may cause a rise of manufacturing costs.
Meanwhile, the prior art has a further problem in that the number of components is increased and manufacturing costs rises since epoxy resins 108 and 109 for fixing the thermistor 102 and the insulating tube 103 for protecting the lead wire 103 exposed to the outside of the air-conditioning case 200 are needed and the lead wire 103 must be formed long.
Furthermore, the prior art has another problem in that a thermal time constant required for transferring heat around the sensor to the thermistor 102 becomes large and a response is deteriorated since the housing 100 of the water temperature sensor 100 is made of only polypropylene, and so, an air-conditioning efficiency is lowered due to imprecise measurement of water temperature.